The use of Near Field Communication (NFC) is becoming common place in applications such as contactless payment systems, security access systems, etc. A typical NFC based system consists of a NFC reader (e.g., Point of Sale terminal) and a NFC device, typically a NFC enabled card or a mobile phone.
Furthermore, a NFC device typically can be configured for either passive load modulation (PLM) or active load modulation (ALM). While, ALM is typically more complex than PLM, components for implementing ALM in a transponder (e.g., a mobile device) can be more compact and, because the transponder utilizes a power source to generate a magnetic field rather than just modulate a magnetic field created by a reader, an ALM transponder can have greater communication distance than a PLM transponder.
In order to perform a transaction using a NFC enabled device and a NFC device in reader mode, the NFC enabled device is brought near the NFC device in reader mode. The communication between the NFC enabled device and the NFC device in reader mode may fail if the NFC device in reader mode fails to properly demodulate the signal from the NFC enabled device. Such failures may occur if the NFC enabled device is not properly aligned with the NFC device in reader mode or if the NFC enabled device is not within a certain distance range from the NFC device in reader mode.
Such failures and other issues can be significantly reduced if there is tuning of the phase offset for active load modulation (ALM) in a NFC enabled device. Therefore, it is desirable to have methods and systems for measuring and compensating the phase offset for ALM in a near field communication (NFC) system.